We investigated the photoreflectance spectra from the space charge region of the model device system indium tin oxide (ITO) on p-InP as a function of reversed d.c. bias Vbias. The period of the observed Franz-Keldvsh oscillations (FKOs) provides a direct optical measure of the surface d.c. electric field ξs. This observation is in contrast with previous electromodulation studies in which the FKOs were related to the modulating a.c. field. From a plot of ξs2 as a function of Vbias we obtained the built-in potential (-0.4 ± 0.1 V) and net carrier concentration. This demonstrates that this technique can be utilized as an optical Mott-Schottky method. The value of the built-in potential is lower than that obtained from previously reported Fermi level pinning studies.
ASJC Scopus subject areas
- Engineering (all)